Length measurement and control in web printing



LENGTH MEASUREMENT AND CONTROL IN WEB PRINTING Filed Jan. 19, 1961 Dec. 8, 1964 M. soRKlN ETAL 5 Sheets-Sheet 1 Dec. 8, 1964 M. soRKlN ETAI. 3,160,758

LENGTH MEASUREMENT AND CONTROL IN WEB PRINTING Filed Jan. 19, 1961 5 Sheets-Sheet 2 C INVENTORS LENGTH MEASUREMENT AND CONTROL IN WEB PRINTING Filed Jan. 19, 1961 Dec. 8, 1964 M. soRKlN ETAL 5 Sheets-Sheet 3 Dec. 8, 1964 M. soRKlN ETAL 3,1

LENGTH MEASUREMENT AND CONTROL IN WEB PRINTING Filed Jan. 19, 1961 5 sheets-sheet `4 Myg F/aa' AAA J AAA.

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ENTORS ATTOR EYS 3,160,758 LENGTH MEASUREMENT AND CONTROL 1N wEB PRINTING Filed Jan. 19, 1961 Dec. 8, 1964 M. soRKlN ETAL 5 Sheets-Sheet 5 wh@ @TWA Q INVENTORS N HMP/.s .sa/rw BY 650,965 ama/ufff@ vte ATTO R N EYS Acircuitry-to help accomplish the foregoing objects. .still further object is to provide circuitry the operation United States Patent() LENGTH MEASUREMENT AND CONTROL IN WEB PRINTING VMorris Sorkin, Bergenlield, and George J. Schowerer,

This invention relates to repeat length measurement and control for a rapidly moving printed web.

Multicolorprinting requires superposed printing of different colors in registration. The printing operation frequently is followed by a converting operation which may be simple rewinding or may be cutting, punching, and creasing as when forming a box blank. Mechanisms including electric eye scanners have been highly developed to secure registration. However, very little has been done in the way of precision measurement of the length of the deviation from desired length of the printed matter along the web. c

Theoretically the print length equals the circumference of the print cylinder. However, the actual length may vary because of factors such as humidity, drying temperature, impression pressure, degree of wetting by the ink,

web thickness, variations in the material ofthe web itself,

and so on.

The general object of the present invention is to measure theV repeat length of printed matter on a continuous web. The apparatus may terminate in an indicatorwhich indicates deviation from' a desired length, and such indication may be watched by an operator and used for manual control of mechanism intended to correct the deviation. If desired, the apparatus may terminate in a vrecorder having a movable pen which makes a continuous record of the repeat length or lits deviation. This may be done when the printed web is rolled up for subsequent use, and only later is unrolled for feed into cutter-creaser mechanism to form a box blank. The written record of repeat length may be kept with the roll and later used as a glide by the operator When feeding that particular roll into the cutter-creaser.

In still another form the apparatus may provide automatic control or correction of deviation, with a view to maintaining a desired repeatlength.

The repeat length is measured between accurately spaced electric scanners. Inasmuch as the repeat length being printed on a web by one printing cylinder may differ greatly from the repeat length being printed on a different web by a different `diameter cylinder, a -urther v object of the ,present inventionis to make this possible without requiring physical movement of one scanner relative to the other. The disclosed apparatus will handle va -wide range of .repeat length, say from 20 inches to 50 inches, while using compact apparatus occupying only a small amount of tloor space, and without requiring any relative movement of the scanners, which. instead are `rigidly mountedin position."

Another object is to select a desired electrical pulse Still another object is @to provide improvedelectrical A of which is independent of changes in rotative speed of .the printing cylinder or cutter-creaser.

ICC

another, as are hereinafter more particularly described in the following specification. The specification is .accompanied by drawings in which:

FIG. 1 is an elevation showing apparatus embodying .features lof the invention;

FIG. 2 is a schematic view drawn to much smaller scale, showing a press line including our invention;

FIG. 3 is a vertical section taken approximately in the plane of the Aline 3 3 of FIG. l;

FIG. 4 represents a remotely controlled reversible motor and a part of its control circuit;

FIG. 5 is a block diagram explanatory of the invention;

FIG. 6 shows the relation between certain signals and scanner pulses used in the circuitry of FIG. 5;

FIG. 7 is a wiring diagram for the power supply;

FIG. 8 is a wiring diagram for 4each of the two scanners;

FIG. 9 is a wiring diagram for the phase micrometer; and

FIG. l0 is a wiring diagram for the computer which receives signals from the scanners of FIG. 8 and the phase micrometer of FIG. 9, and which controls an indicator or/and recorder or/and correction mechanism.

Referring to the drawing and more particularly to FIG. 2, a web 12 is fed from a web roll 14 by means of a power driven feeding unit 16. The web is supplied to a multicolor gravure press line which in this case comprises gravure press units with overhead dryers, indicated at 18, 20, 22, and 24. The web is then fed by a pull unit u26 to a roll 28. However, it could go `directly to a cuttercreaser. In accordance with the present invention, the repeat length is measured by apparatus shown at 30. This may be placed in any hdesired (location, and in the present case c may be remotely located.

For automatic control of the repeat length we `here v,show mechanism which varies the web tension. Specifically, the web is formed into a loop around a roll 32 located somewhat like a dancer roll, but in this case subject to force supplied by an air cylinder 34. The air pressure supplied to the cylinder 34 is controlled by a regulatorvalve 36, lthe adjustment of which is varied by a reversible remotely controlled motor 38. The apparatus 30 and more specically the computer 9i) controls the reversible motor 3S, but such remote control may be applied to other means for varying repeat length. For example, the tension may be varied b y mechanism shown in patent application No. 682,958 `tiled September 9, 1957, and entitled Variable Web Tension for Uniform Layoti, since issued on March 20, 1962, as Patent No. 3,025,791, or the repeat length may be varied by changing compression ofthe web as in application SerialfNo. 688,034, `tiled October 3, 1957, and entitled Multicolor Printingon a Continuous kWeb, since issued on February 2l, 1961, as Patent No. 2,972,297, both tiled by George N. Auerbacher.y

In accordance with usual practise, the press units are all driven from a common line shaft 40. A registration means, not shown, usually of the planetary diti'erential gear type, is provided `between the line shaft and each press unit. The line shaftj40 also drives the feed Vrolls at -16 andthe pull rolls at 26, but preferably through variable speed drives such as aV Reeves or a PIV drive indicated at 42. For pulse selection, described later, the line shaft 40 also drives a phase micrometer indicated at 44.

The repeat length measurement unit Aindicated at 30 in FIG. 2 is shown in detail in FIGS. l and 3 of the drawing. Referring there, the web 12 passes over a fixed roll 46, a movable roll 48, and another fixed roll 50, which together form a, loop of web having parallel sides 52 and 54. A web scanner 56 is located at Xed roll 46, and a second web scanner 58 is located at the other fixed roll 50. The roll 48 is mounted for adjust-` ment of its position along a plane bisecting the space between the sides 52 and 54 of the loop, thereby adjusting the length of the web between the scanners. In the present case the movable roll 48 may move between a bottom position shown at 48 and a top position shown at 48. This provides a very wide range of adjustment, which in the specific machine here shown extends from twenty inches to fifty inches of repeat length. n

A scale 6G and pointer 62 are relatively moved when the roll 48 is moved, and the scale 60 is preferably marked in terms of the repeat length between the scanners 56 and 53. The sides of the loop 52 and 54 are `kept parallel so that the scale may be a uniform one.

The means for adjusting the position of the movable roll is best shown in FIG. 3, and comprises upright spaced screws 64 and 66 at the ends of the movable roll 48. The screws carry the bearings 68 and 70 of roll 48, and the two screws are geared together for simultaneous equal rotation. t

More speciiically, the upper end of screw 64 carries a mitre gear 72, and the upper end of screw 66 carries a similar mitre gear 74. These mesh with mitre gears 76 and 78, which are both carried on a horizontal shaft eter signal, and the scanner pulses is indicated in FIG. 6. The live gate 118 has a desired length, which in the present case is approximately ten degrees out of the full'rotation of 360 degrees. This gate is shown rectangular in lform, but it could vary at the forward andrear edges.v l

The selection ofy the correct yscanner pulses from among others along the printed matter is accomplished v by requiringcoincidence with the live gate 118, as indicated at 148 in FIG. ,5, by means of circuitry subsequently described. vThe pulse from one web scanner is shown at y120, and that from the other is shown in broken lines at 122. Actually the scanner pulses are used to trigger sharp pick-oli pulses, `and, these are what is shown at 120 and 122. When the repeat length is correct, these pulses are simultaneous, but when there is a deviation they become separated, as shown.

80 which is rotatable by meansof a crank 82. For comf pactness the mitre gears 76 and '78 may facein opposite direction, and therefore turn the screws 64 and l66 iny opposite direction, in which case one has a right hand and the other a left hand thread. Y Y

1f desired, the bearings 68 and 70 may be accurately guided by the sides of the frame, in addition to being carried by the screws, in which case the latter would serve primarily to change ythe heightof the bearings,`

n peat length is correct, and are here slightly displaced However, because the sides y52 and S4 of the loop of web are parallel, the bearings may be supported solely by the screws 64V and 66, there being no sideward force.

A block diagram for the circuitry is shown in FIG. 5

of the drawing. The web lscanners are indicated at 56 and 58 located above the fixed rolls 46 and 50. The' lscanners include localized amplifiers, and the` output is n special mark'on the web, by selecting a desired .pulse from among many, a phase micrometer is employed. This consists of'a shallow cup or cylinder 96 driven oneto-one with the printing cylinder (or knife, in the case of a cutter-creaser) by means of a shaft 98. This may be driven conveniently by a chain` or gearing or ktiming belt from the line shaft. There is a light source lampl 'inside the cylinder, and twophotoelectric cells 102 and 104 outside the cylinder, together with appropriate lenses, etc., inside and outside thecylinder. Thisentire assembly is in a protective, housing which is rotatively adjustable to establish any needed phase position.-

The cylinder has aperturesk or slots which are yapprox# One system supplies a live'gate oncerper" revolution which is fed through line 106 to. a web'fpulse selector 108. The other provides a micrometer signal once perv revolution which is fed through line 110 to a micrometer regulator 112. This has two like outputs supplied to cathode followers, indicated at 114 and 116.

The Ltwo micrometer signals provided at 114 and 116 in FIG. 5 are indicated by the solid and dotted lines at 124 in FIG. 6. The wave form has a sloping edge, and the potential ofthe micrometer signal at the instant of the pick-off pulse is indicated by a solid line at 126. Thispotential is .ameasure of the timing of the pick-oil pulse triggered by `a scanner pulse. The two micrometer signals in fact are truly coincident when the reonly to show that there are two of them. In the case here shown the delay of pick-off pulse 122 is indicated by the height of the dotted line 128,relative to the reference solid line 126. Increased deviation-increases the spacing, and a deviation in opposite sense (shortened 'instead of lengthenedrepeat length) would bring the dotted line 128 below the reference line 126. Reverting now to FIG.l 5, the micrometer regulator 112 gives the micrometer signal a desired wave shape and size and provides two equal and isolated outputs, which are supplied to the cathode followers114 and 116 which '.then lead to pickoi'circuits 144 and 146. It will be recalledthat the live gate was supplied at 106 to the web pulse selector 108. The scanner pulse from amplier 92 is combined with the live gate, and the scanner pulse from amplifier 94 also is combined with the live gate, with resultingwave formy indicated at 148. This raises the selected pulse, relative to` other pulses received outside the live gate, that is during almostall of the rotation of the printing cylinder. The subsequent circuitry, in this particular case a thyratron tube, requires the said increased voltage of the selected pulse, for tiring.

It will be seen that one micrometer signal is combinedv with one selected pulse in pickoff circuit 144, while the other micrometer signal is combined with the'other selected pulse in` pickotl circuit 146. The outputs of the pickoi circuits'arecombined in ak differential amplifier which `results in a signal which is positive-going for' a deviation in one direction, negative-going for a deviation in an opposite direction, and thepotential of which depends onthe amount of deviation. v

This may be used in any or all of three ways. One is in a meter which indicates deviation, and this is shown locally at M and remotely at 152. Another is to record the deviation `on a moving sheet of paper, and this is shown at 154. In the present case a combined meter is The mechanical arrangement of the phase micrometer 'i 96 (and of the scanners 56 and 58) need not be used, that here,v shown being atypical commercially availi able instrument such as that made by the Esterline-Angus `Company Inc., of Indianapolis, Indiana, but other such indicator-'recordery meters may be used.

n The output of the dilierential amplifier 150 also may be used in an automatic correction circuit 155, which typically has a three-wire output indicated at 156 to control a remote reversible motor. In the present case such .5 a motor is indicated at 38 in FIG. 2. One example of Wiring for such a motor is schematically represented in FIG. 4 of the drawing. It will be understood that the motor control may be through relays, as indicated at 190 and 192 in FIG. 4, leading to the motor 38. Pilot lights may be provided, indicated at I1 and I2, which may differrin color, say green and red respectively, to show the direction in which correction is being made.

The electrical circuitry is next considered in greater detail. A suitable form of power supply is shown in FIG. 7. It is energizedfrom an A.C. supply line under control of a switch S4. This leads to a transformer having two primaries with four leads so that they may be connected in parallel, as shown, for use with a 115 volt supply, and in series for use with a 230 volt supply.

A full wave rectifier circuit centers about the tube V18, which may be a type 5V4GTB. The secondary provides 1000 volts center tapped for the anodes of this full wave rectifier tube, and the filament is heated at 5 volts. Series inductors and shunt capacitors provide a suitable filter, so marked. The` tubes V15, V16, and V17 are voltage regulator tubes. B supply is provided at 75, 150, 225, 245, and 400 volts, as indicated on the drawing.

Additional low voltage secondaries with center taps provide a number of independent supplies for iilament heating at 6.3 volts, the first, indicated at 130, having its center tap at ground potential; the second, indicated at 132, having its center tap at 225 volts; and the third,

indicated at 134, having its center tap at 150 volts. Supply 130 is used for the lilaments of later-described tubes V1, V1-1,`V2, V3, V3-1, V4, V6, V8, and V19. Supply 132 is used for the iilaments of tubes V5, V5-1, V12 and V13. Supply 134 is used yfor the laments of tubes V9, V10, V11, and V14. i

To energize the light source lamps, a high density selenium rectifier is provided at 136, this being supplied from a secondary with a tap switch at S5. The circuit is intended to deliver a filtered D.C. to the remote light source lamps, with a potential of 11 volts at the lamps, regardless of voltage drop in the long lines leading from the power supply to the lamps. The tap switch S5 is provided to cornpensate for any such voltage drop in different installations, and to provide the desired voltage at the lamps.

The two web scanners are alike and have the same wiring diagram. This wiring diagram is shown in FIG. 8 of the drawing. The light source lamp is indicated at I-100 and may be a type #1327. The photoelectric cell is indicated at V100 and may be a type 929 photocell. A pulse developed by the photocell is applied to an amplifying tube V101. This is a dual tube with one grid connected to one side of the photocell, and the other connected to the other. The tube anodes are connected to a single pole, double throw switch S100, which is used to white, or white on black, so that the resulting pulse may be either positive-going or negative-going, and the switch S100 is appropriately set to provide a negative-going pulse.

This pulse is fed to the grid of one half of an amplifiertube V102, the output of which is an amplified pulse which is now positive-going. This is fed to the grid of the other half of tube V102, which is connected to a cathode resistor and acts as a cathode follower. The said cathode resistor is not shown in FIG. 8 because itis located in the computer shown in FIG. 10. The purpose of the cathode follower is to provide a low impedance output, matching a low impedance line extending all the way from the scanner to the computer, and to make it feasible to use an ordinary or non-,shielded line for delivery of the web scanner pulse, indicated at 136. The other connections shown on terminal strip 138 are for .ground and for filament andV B voltages. Tube V101 may be a type 5814WA, and tube V102 may be a type 6 6201, their heater filaments being shown at 137. The 'conductors leading from terminal strip 138 terminate at their far end in a multiple prong connector for connection to a receptacle in the computer circuitry.

The circuit for the phase micrometer is shown in FIG. 9. The light source lamp I- corresponds to that shown at 100 in FIG. 5, and may be a type 1327. It serves two optical systems, one of which terminates in photoelectric cell V200, and the other in photoelectric cell V201, these being type 922. The output of cell V200 is the sloping or micrometer gate (shown at 124 in FIG. 6), and is applied to the grid of one half of the tube V202, which may be a type 5814WA. This is' connected and used as a cathode follower. The output of cell V201 is the live gate (shown at 118 in FIG. 6), and is connected to the grid of the other half of tube V202, which is also connected and used as a cathode follower.

inasmuch as the normally fixed parts of the entire phase micrometer head are rotatably adjustably adjust-able, to establish any desired phase relation to the print cylinder, the connections preferably are made through slip rings which are schematically indicated in superposed relation at 140. These lead to a terminal strip 142, and conductors from this extend all the Way to the computer where they terminate in a multiple prong detachable connector for connection tot a receptacle in the computer circuitry.

The purpose of the different conductors is clear from the drawing, the upper conductor providing a low voltage supply for the light source lamp and the heater filament shown at 144 for the cathode follower tube V202. There are conductors for the 225 volt and 75 volt B supplies for the tube and for the photocells respectively, and for a ground connection, as well as a conducto-r for the live gate and another for the micrometer signal.

It may :be mentioned that in the particular circuitry here shown the live gate has a base line at 62 volts and goes up to 78 volts, and the micrometer signal has a base line at 72 volts and goes up to 80 volts or more.

The circuitry of the computer is shown in FIG. l0 of the drawing. The bundle of conductors from the phase micrometer terminates in a plug received in a receptacle 170, shown at the bottom left. The live gate is indicated at 172, and is supplied to the cathodes of the righthand half of the tubes V113 and V1-1 (the B half). In these tubes the live gate combines with the desired pulse from each of the two scanners. The bundlel of Wires from the scanners terminates in a plug received in a scanner receptacle 174, shown at the upper left. The pulse from one scanner is supplied to the grid of tube VlA, and the pulse from the other scanner is supplied to the similar left grid of tube Vl-l. i

The micrometer signal leaves receptacle on conductor 176, and is regulated to desired shape and dimension, and is' divided to provide two like and isolated outputs in the group of tubes V2, VSA, V4B, and V3-1A, the latter two being used as cathode followers which provide the desired dual output indicated at 178 and 180.

The computer selects the desired pulse as follows. Pulses coming from one web scanner are capacitively coupled to Vthe grid of tube V1A (one half o-f a type 6SL7 tube). The resistor of the cathode followertube in the scanner (the right half of tube V102 in FIG. 8) is shown at R1. This stage is normally cut off by a +2.5 or +4.0 volt bias, depending upon the position of switch S1. Positive pulses on the grid cause plate current to flow through resistor JRS, dropping the plate voltage. This drops the grid of tube VlB below +75 volts.

The cathode of tube V1B receives the live gate signal, its voltage changing between +62 volts when the live gate is closed to +75 volts when the live gate is open If a grid pulse occurs While the `live gate is closed, or yif the live gate is openf Without a simultaneous grid pulse, ythe plate current of tube V13 is reduced but not .to cut olf, the flow of current producing a voltage drop across resistor R19. However, if a grid pulse occurs while the gate is open, the plate current of tube V1B is cut off, causing the plate to rise to +245 volts. This rise becomes the selected web pulse, shown at 175 and 177, which is fed to the pick-olf pulse generator tube V and to the control grids of lengthen and shorten relay control tubes V12 and V13. Tubes V5, V5-1, V12

The pickoff pulse is a sharp kpulse located coincident with.

the leading edge of the selected web pulse (the latter being suggested at 175 and 177). The tubes V5 and j V5-1 are thyratrons, and are normally cut off by the negative bias present on both grids. During this time the capacitor C charges up to the +400 volts supply voltage. When the selected web pulse turns on the plate current, the capacitor C26 discharges through tube V5, producing a current pulse of `high amplitude andjvery short duration through the primary of the transformer T2. This causes voltage pulses a few microseconds long to appear across the transformer secondaries.

The secondary windings are connected in'series with a neon glow lamp I4 (typeNESl in this instance), and across a diode switch circuit consisting of four-silicon diodes (type l`N4579) in bridge formation indicated at SRV.

When the voltagereaches the ionization potential of neony lamp I4 a current pulse a few microseconds long flows through the diodes. The lamp I4 acts as a high frequency switch which breaks down for the selected pulse. This effectively closes the circuit between themicrorneter j signal andk the capacitor C21, causingthe capacitor to charge up to the voltage which the regulated micrometer signal has reached at the instant of the picked' pulse. The capacitor charges only to the Voltage existing at the instant of the pulse on the sloping side of the micrometer signal. This description applies alsoto the-lower circuit following tube VS-l for other scanner` pulse.

After the picko-l" pulse, the capacitor C21 is disconnected from `the micrometer signal, and its voltage rcmains at the picked olf value until the next pulse. pacitor.- C21 is connected to the grid of a'cathode follower tube VSB (or V3-1B for the similar lower circuit). The cathode current flows through R56 and R57. to ground. Tube V3 is a type 5691. The resistors R56 and R57 are proportioned (in thiscase 2K and 160K ohms) so that the junction will be at +75 volts when the grid is at +75 volts. The voltage at this junctionk becomes the proportional control voltage for the deviation circuits, that is, circuits which respondto'd'eviation. The capacitor voltage will siowlyfreturny to +75 volts (which here has a Value of 100M).

+75 volt reference value when thepress `is stopped.

The micrometer regulator automatically controls the waveform and peak voltage of the micrometerl signal at` micrometer signal, and is fed to the grid of a cathode follower V2B, causing its cathode to follow. The cathode resistor of V2B also is a voltage divider. The junction voltage controls the grid of a tube VSA (a type 5691 tube) whose plate is connected to the resistor R38 by a conductor 182. Therefore, the micrometer signal is regulated or stabilized because any drop in the generated micrometer signal is counteracted by a decrease in the plate current of tube VSA.

Coming back now tol the'utilization ofv the pickoff proportional control voltage, that from cathode follower VSB is connected to one grid of tube V8, a type 6SL7G tube operating as a dilference amplifier. Similarly that from the cathodefollower V3-1B is connected to the other grid of tube V8 for the other pickof't. Consequently deviation from correct repeat length is manifested asan unbalanced output. The output is taken from r'the twoplates of tube V8` in push-pull, one plate voltage rising when the other falls. With perfect repeat length, there is balanced output from the dilference amplier V8.

The outputs are direotlyc'oupled to` the grids of tubes V9A and V9B, a type 6SL7B tube operating as a dual cathode follower. The cathode current of tube V9A ilows through a voltage divider connected from the cathode to ground, and the output is takenfrom the junction f of itsdivider.

The voltage between these dividers, that is, the relative voltage, is a measure of the instantaneous repeatlength deviation. With the signal selector switch S-6 in the left position shown, the output to receptacle 184 rgives this voltage as an instantaneousvoltage. The re- The output of thistube is also taken from cathode voltage dividers; one output from one junction; and the other from the other junction. The voltage between these two junctions is a measure of an average deviation, which may be fed to receptacle 184 and thence to vindicator recorder 31 when switch S6 is in the middle position.

The tube V9 (A and B) provides the instantaneous deviation signal. The -tube V10 (A and B) in conjunction with the integrating resistance-capacitance networks connected to their-grids, provides the average deviation signal. VIf automatic correction is provided, additional circuits leading to relays are used. The averaged directional control Voltage from tubes V10A and V10B is fed by conductors 186 and 188 into a 6SL7 type dual triode marked V11. With no repeat length deviation, both sections of the tube are conducting, and both plates are at +185 volts. With repeat-length deviation one grid goes negative and the other positive. When a grid goes suciently negative theplate current of that section is cut olf and the plate voltage rises to +225 volts. The amount that the grid goes negative before it cuts off the plate current j depends upon theV settingpof a controlV potentiometer C1.

This potentiometersfets the cathode voltage on tube V11,

yand ythus establishes the tolerance or minimum deviation Y above which a correction takes place.

the left center junction of silicon diode bridge SR. The

micrometer signal input at receptacle 170, coming from the phase micrometer, is fed through a one megohm resistor R38 to the grid of the 'cathode followers V2A (a type 6SL7 tube) and` V43 (a type 569].WA tube). The cathode resistor of tube V2A is :a voltage divider leading to tube VdA. The tube VAris connected grid to anode to act as a diode, and is connected between the junction of the voltage divider beneath tube V2AV and a capacitor C19, the latter being in parallel with ya resistor R41. The diode charges the capacitor when the micrometer signal exceeds Volts. The capacitor voltage represents the maximum voltage of the Vgrid at its cathode voltage.

When the'left sideof tube V11 is cut off, its plate Voltage rises to +225 volts and this voltage is fed to a control grid of a type 2050 thyratron marked V12, putting this However, the thyratron is still cut off by the negative bias on its other control grid. If, however, the selected web pulse is applied simultaneously to the -other control` grid, the thyratron conducts and remains conducting until itsplate circuit is opened. When this thyratron conducts, thenlengthen relay is energized, its contacts in the correction system are closed, a green correction lampIl is lit on the computer panel, and a duplicate green lamp is lit at the correction unit o1' wherever desired. If the apparatus is being used for siennes 9 automatic operation the correction motor is energized for a lengthen correction, lthe connection being made through receptacle 184.

A suppressor network consisting of R22 and C14 may be connected across the relay contacts to prevent arcing. A butter condenser may be used -to prevent transient voltage surges from getting into the power supply.

Similar operation takes place when the plate current of the right half of tube V11 is cut oit, except that the thyratron tube V13 conducts; the -shorten relay 192 is energized; the red correction lamp I2 is li-t `on the correction computer and at the correction station; and the correction motor is energized for a shorten correction.

The thyratron V12 or V13, once conducting, remains conducting, and must be cut oft, which is done by a correction timing circuit. 'Ihe length of correction is determined by the instantaneous deviation, while the direction or sense of the correction is determined by the average deviation.

The correction timer input voltages from the instantaneous deviation circuit are fed through conductors 196, 198 into an RC timing network consisting of resistors R24, R25, and capacitors C17, and C18. Capacitors C17 and C18 charge up to these input voltages. Both the lengthen and shorten relays 190 and 192 energize a set of additional relay contacts in the proportional timing circuit, these relay contacts being shown at 190 and 192'.

As previously described, it is the control potentiometer voltage which goes negative from 150 volts which controls the direction of the correction. When either the lengthen or shorten relay is energized its corresponding timing capacitor C17 or C18 is charged negatively with respect to 150 volts, and this voltage is placed on the left grid of a tube V14 (a type 6SL7) tube. This grid voltage then rises linearly as the capacitor, either C17 or C18, starts to charge upto +225 volts. This controls the right halt of the tube V14 which controls the coil of a timing relay 194. (Its contacts 194 are shown at the right of relay 192.)

As the grid voltage rises it reaches a point where the tube V14 conducts and the timing relay 194 is energized, and its contacts 194' are pulled in. The voltage at which the tube conducts depends upon the setting of control potentiometer C1, previously mentioned. The time interval determined by the linear rise in grid voltage is proportional to the instantaneous deviation.

The timing relay 194 opens the plate circuit of the thyratron, cie-energizing the control relays` (either 190 or 192 as the case may be). This also resets the averaging circuit at the tubes V9 and V10, through the closing of contacts 194 of relay 194 (shown near tube V10A). The cie-energized control relay (190 or 192) in turn resets the timing circuit. Of course the correction at the correction motor stops.

The rotary variable resistor 200 is used to compensate for different sizes (diameters) of printing cylinder. The said resistor is connected in series with the indicator recorder 31. The germanium diode bridges 33 in FIG. 10, shunting the meters M, are used to protect the meters from surge currents.

The parts shown at 202 in the scanner pulse supply lines are transistors used as diodes t'o eliminate all negative-going pulses. The rectitiers shown at 204 are silicon diodes, type IN459 which are used as a clipper which cuts oi the positive going pulse above the bias, that is, the tube responds to the pulse but does not feel the shock of a high voltage. The silicon diode 205 is used to clip the live gate signal at the desired voltage, in this case 75 volts.

The three position switch S6 makes it possible to operate the indicator-recorder 31 in response to either instantaneous deviation or average deviation lfrom correct repeat-length. The correction circuitry centering around tubes V12, V13 `and V14, for control of a correction motor, responds to both instantaneous and average deviation,

10 in that the direction or sense of the correction depends upon the average deviation, but the amount of the correction depends on the magnitude of the instantaneous deviation as the correction is being made.

There is a third position of switch S-6, this being the position furthest to the right in FIG. 10. It is used to show on the indicator-recorder the adjustment of the potentiometer C1, or in other Words, to show the tolerance positionk to which the correction circuit is set. It shows that value of deviation above which the correction circuit will function or come into operation to cause a correction.

The short lines 210 and 212 for the scanner puises are shielded inside the computer, as shown at the upper left in FIG. 10, but this precaution is not needed for the long external lines from the scanners.

The combination of the sharp pick-oft pulse triggered by the selected web scanner pulse with the micrometer signal is shown at `179 and 181 in FIG. l0. The loading effect of current flowing in capacitor C21 at the instant of pick-oif pulse is shown by the break in the waveform of the sloping edge. At the same conductors, the micrometer signal is shown at 178 and 130 in the absence of a pick-oit" pulse as when the system is not properly phased.

It is important throughout the circuitry shown to provide for isolation of each stage from other stages. An undesired relation may be established through a common B-plus supply, or a common tube. For example, in FIG. 1() the cathode followers V4B and V3i-1A serve to isolate one micrometer signal from the other. Also the bridge SR in combination with the neon lamp14 serve to eliminate all voltages except the voltage at the instant of the pick-oli pulse. To make that voltage useful it is used to charge a capacitor, and thus the voltage on the capacitor becomes an indication of repeat length, as described in connection with lines 126 and 128 in FIG. 6.

There is an important advantage in using a micrometer signal with a sloping waveform, combined with a pick-off pulse or pip which shifts in location along the slope, to determine a voltage relative to a reference voltage, in lieu for example' of a measurement of the time interval between tw'o scanner pulses. In the latter case diiiiculty would arise in the event of a change of rotative speed of the print cylinder or press being used.l This is so because a time difference would not be in linear relation to a physical change in repeat length. The same time difference would represent a larger error in repeat length,

when a press is 'running faster. However, with the present circuitry there is automatic compensation, because the slope of the micrometer signal is itself produced by the rotation of the phase micrometer (96 in FIG..5) and changes automatically with a change in speed. At higher speed the slope is steeper with respect to time (though unchanged with respect to the rotating cylinder). Referning to FIG. 6, with a steeper slope the same voltage dierence between lines 126 and 128 is produced by a smaller time difference between pulses. Because of this the present circuitry performs correctly independently of the speed of operation of the equipment.

It will beunderstood that although specic tube types and components and specific voltage values, etc. have been given in the foregoing description, these have been set forth for convenience and by way of example, Iand are not to be considered in limitation of the invention.

It is believed that the construction and operation of our apparatus for length measurement and control in web printing, as well `as the advantages thereof, will be apparent from the foregoing detailed description. The scanners may be rigidly and ixedly mounted in compact or close spacing, and yet the effective distance therebetween, that is along the web, may be readily and accuratey ly and widely varied, in this case over a ratio of two and one-half to one. The measurement of deviation from correct repeat length may be used to indicate the deviation, or to record the deviation, or to correct the deviashown.

It will be apparent that while we have shown and described our invention in a preferred form, changes may be made, without departing from the scope of the invention, as sought to be defined in the following claims.

We claim:

y l. Apparatus for repeat length measurement in web printing by means of a print cylinder, said, apparatus comprising a first optical photoelectric scannerffor scanning a marker on a moving web to produce an electrical pulse, a second scanner for scanning the same marker at the correct distance or" one or more repeat lengths from the first scanner toy produce a second electrical pulse, means geared to said print cylinder forproducing a micrometer signal having a sloping portion'at the location of the marker, electronic circuitry for combining the pulses with themicrometer signal, and means utilizing the relative displacement of the pulses along the sloping portion of the micrometer signal,v kas a measure of deviation from correct repeat length. y v

2. Apparatus for repeat length measurement in webl printing by means of a print cylinder, said apparatus comprising a first optical photoelectrcal scanner for scanning a marker on a moving web to produce an electrical pulse, a second scanner for scanning the same marker at the correct distance of oneor more repeat lengths from the rst scanner to produce a second electrical pulse, means geared to said print cylinder for producing alive gate at the approximate location of the marker, additional means geared to said print cylinder for producing a micrometer signal having a sloping portion at the location of the marker, electronic circuitryfor so combining the pulses and the live gate as to effectively eliminate all other pulses produced elsewhere along the web, electronic circuitry for combining the resulting selected pulses with the micrometer signaLand electronic circuitry to compare the relative position 'of said pulses along the sloping portion of the micrometer signal, as a measure of deviation from correctrepeat length. f p i y l 3. Apparatus for repeat lengthrmeasurement in web printing by means of a print cylinder, said apparatus comprising a rst optical photoelectric scanner for scanning a marker on a moving web to produce an electrical pulse, a second scanner for scanning the same marker at the correct distance of one or more repeat lengths from the first scanner to produce a4 second electrical pulse', means geared to said print cylinder for producing a to chargethe same with a voltage dependent on the location of one Vpulse along said sloping portion, a second capacitor and means to charge the same with a voltage dependent on the location of the other pulse along said sloping portion, a difference amplifier, means to apply said capacitor volt-ages to said difference amplifier, and means tok utilize the resulting difference signal as a vmeasure ofdeviation from correct repeat length.

5. Apparatus for repeat length measurement over a widerange of say two to one, in web printing by means of a print cylinder, said apparatus comprising two fixed rolls and a third Vmovable roll which together form a loop of web having parallel sides, a first optical photoelectricweb scanner located at one fixed roll for scanning-a marker on a moving web to produce an electrical space between the sides of the loop and thereby adjusting the length of the web between the scanners, a long scale and a pointer relatively moved by the movable roll and marked in'terms of the actual repeat length between the scanners, electronic circuitry to compare the relative timeof occurrence of said pulses, and means to utilize a resulting departure from simultaneous occurrence as an indication of deviation from the repeat length indicated by the scalej and pointer, whereby the position of the movable roll whenv changed to obtain sumultaneous occurrence of said pulses provides a direct measurement by the scale and pointer of a repeated length marked on the movable web.

6. Apparatus for repeat length measurement over a wide range of say two to one, in web printing by means of a print cylinder, said appanatus comprising two fixed rolls and a third movable roll which together form a loop of web having parallel sides, aptirst optical photoelectric -web scanner located' at one fixed roll for scanning a [marker on a moving web to produce an electrical pulse, a

vto produce a second electrical pulse, means mounting the @movable roll for precision adjustment of its position for fa long distance along a plane bisecting thespace bemicrorneter signal having a sloping portion at the loca` v tion of the marker, electronic circuitry for combining the pulses with the micrometer signal, a.l first capacitor and means to charge the same with a voltage dependent on the location of one pulse along said sloping portion,

a second capacitor and means to charge the same with j a voltage dependent on the locationof the other pulse along said sloping portion, a difference amplifier, means comprising a r'st optical photoelectric scanner for scan-kr ning a marker on a moving web to produce an electrical pulse, a second scanner for scanning the same marker at the correct distance of one or more repeat lengths from the first scanner to produce av second electrical pulse,

means geared to said print cylinder for producing a `live gate at the `approximate location of the marker, additional means geared to said print `cylinder for producing -a micrometer signal having a sloping portion at the location of the marker, electronic circuitry for so combining the pulses and the live gate as to effectively eliminate all'other pulses produced elsewhere along the web, electronic circuitry for combining the resulting selected pulses with the micrometer signal, a first capacitor andA means tween the sides of the `loop and thereby adjusting the l length of the web between the scanners, a long scale and a pointer relatively moved by the movable roll and marked in terms of the actual repeat length between the scanners, the means for adjusting the position of the movable roll comprising spaced screws at the ends of the yroll carrying the bearings thereof, and means gearing the screws together `for simultaneous equal rotation, electronic circuitry to compare therelative time of occurrence of said pulses,y and means to utilize a resulting departure from simultaneous occurrence as an indication of deviation from the repeat length indicated by the rmovable web.

y'7.,Apparatus for repeat vlength measurement in web printing by means'of a print cylinder, said apparatus compris'ing two fixed rolls and a third movable roll which signal, and means utilizing the relative displacement of the pulses along the sloping portion of the micrometer signal, as a measure of deviation from correct repeat length.

8. Apparatus for repeat length measurement in web printing by means of :a print cylinder, said apparatus comprising two fixed rolls and a third movable roll which together form a loop of web having parallel sides, a fixed photoelectric optical web scanner located at one lixed roll for scanning a marker on a moving web to produce an electrical pulse, a second web scanner located at the other xed roll for scanning the same marker at the correct distance of one or more repeat lengths from the first scanner to produce a second electrical pulse, means mounting the movable roll for precision adjustment of its position along a plane kbisecting the space between the sides of the loop and thereby adjusting the i4 length of the web between the scanners, a scale and a pointer relatively kmoved by the movable roll and marked in terms of the repeat length between the scanners, the means for adjusting the position of the movable roll comprising spaced screws at the ends of the roll carrying the bearings thereof, and means gearing the screws together for simultaneous equal rotation, means geared to said print cylinder for producing a micrometer signal having a sloping portion at the location of the marker, electronic circuitry for combining the pulses with the micrometer signal, and means utilizing the relative displacement of the pulses :along the sloping portion of the micrometer signal, as a measure of deviation from correct repeat length. l

References Cited in the file of this patent UNTED STATES PATENTS 1,970,352 Wohlrabe Aug. 14, 1934 2,081,654 Wohlrabe May 25, 1937 2,278,933 K0ttf- Apr. 7, 1942 2,289,737 Sorkin July 14, 1942 2,529,161 Kelling et al.` Nov. 7, 1950 2,632,855 Bendz Mar. 24, 1953 2,994,783 LOoschen Aug. l, 1961 

1. APPARATUS FOR REPEAT LENGTH MEASUREMENT IN WEB PRINTING BY MEANS OF A PRINT CYLINDER, SAID APPARATUS COMPRISING A FIRST OPTICAL PHOTOELECTRIC SCANNER FOR SCANNING A MARKER ON A MOVING WEB TO PRODUCE AN ELECTRICAL PULSE, A SECOND SCANNER FOR SCANNING THE SAME MARKER AT THE CORRECT DISTANCE OF ONE OR MORE REPEAT LENGTHS FROM THE FIRST SCANNER TO PRODUCE A SECOND ELECTRICAL PULSE, MEANS GEARED TO SAID PRINT CYLINDER FOR PRODUCING A MICROMETER 